Engineering topics
Publications and source records attributed to Cramer, D. B..
Weightlessness produces significant physiological changes. Whether these changes will stabilize or achieve medical significance is not clear. Artificial gravity is the physiological countermeasure, and the tether system represents an attractive approach to artificial gravity. The need for artificial gravity is examined.
The optimization of human productivity on the space station within the existing resources and operational constraints is the aim of the Human Productivity Program. The conceptual objectives of the program are as follows: (1) to identify long lead technology; (2) to identify responsibility for work elements; (3) to coordinate the development of crew facilities and activities; and (4) to lay the foundation for a cost effective approach to improving human productivity. Human productivity work elements are also described and examples are presented.
Previous fundamental research in space life sciences is examined, and consideration is devoted to studies relevant to Space Station activities. Microgravity causes weight loss, hemoconcentration, and orthostatic intolerance when astronauts returns to earth. Losses in bone density, bone calcium, and muscle nitrogen have also been observed, together with cardiovascular deconditioning, fluid-electrolyte metabolism alteration, and space sickness. Experiments have been performed with plants, bacteria, fungi, protozoa, tissue cultures, invertebrate species, and with nonhuman vertebrates, showing little effect on simple cell functions. The Spacelab first flight will feature seven life science experiments and the second flight, two. Further studies will be performed on later flights. Continued life science studies to optimize human performance in space are necessary for the efficient operation of a Space Station and the assembly of large space structures, particularly in interaction with automated machinery.
The antimotion sickness remedy, transdermal therapeutic system-scopolamine, administered in this experiment was scheduled to deliver 1.0 mg of scopolamine over a period of 3 d, and this paper compares its efficacy 12 and 72 h after administration. In a double-blind study, six male college students were individually exposed to a standardized provocative test in a slow rotation room after six apparently identical treatments comprising four placebos and two medications. Efficacy was categorized as beneficial, inconsequential, or detrimental. None of the responses was detrimental. Following the first administration of the therapeutic system, there were four beneficial responses after 12 h but none was beneficial after 72 h. Following the second treatment regimen, there were four beneficial responses after 12 h and three beneficial responses after 72 h. Great individual differences were demonstrated, two subjects accounting for six beneficial responses and two accounting for only one beneficial response. The difference in efficacy after 12 and 72 h has practical and theoretical significance.
The events leading up to Spacelab mission 4, which is to be dedicated exclusively to life sciences experimentation in 1984-85, are described. Out of 400 experiment proposals initially received and assessed, 87 candidates were chosen for definition studies to identify the resources which would be required. These proposals addressed such problems encountered in previous space flights as space motion sickness, cardiovascular deconditioning and muscle wasting, calcium loss, and red cell mass reduction. Additional experiments were selected from bioengineering, plant physiology, and cell biology. Human subjects will consist of a Mission Specialist Astronaut and up to four Payload Specialists. Equipment to be used in experimentation includes biotelemetry systems, microscopes, cameras, centrifuges and refrigerators, all of which have been designed for use in weightless conditions. The 87 candidate experiments will be further reduced to about 20.
A double-blind, placebo-controlled study compared the efficacy of transdermal therapeutic system-scopolamine administered alone and combined with ephedrine sulfate given orally in doses of 12.5, 25, and 50 mg. Eight normal male students were exposed to stressful accelerations in a slow-rotation room after receiving 10 apparently identical treatments comprising the four drugs and six placebos. Efficacy of the drug was defined in terms of the placebo range and categorized as beneficial, inconsequential, or detrimental. None of the effects was detrimental. Overall beneficial effects were 60% for transdermal therapeutic system-scopolamine (plus placebo) and 57% for the three transdermal therapeutic system-scopolamine plus ephedrine combinations.
Two flight students, grounded for the reason they were highly susceptible to motion sickness, completed their training after gradually adapting 10 rpm, achieved by executing head movements during small stepwise increases in angular velocity. Subject 1 executed a total of about 77,000 head movements within a period of five months and Subject 2 executed about 108,000 head movements within a period of 42 days. The transfer of the adaptation acquired in the laboratory to most motion environments aloft was good; the notable exception involved weightless maneuvers in the case of Subject 1. Both were on flight status when contacted recently. The current motion sickness susceptibility in Subject 1 in the fall of 1975 was assessed. He reached a (mild) motion sickness endpoint, in the rotating room, at 17 rpm; the average endpoint is 7 to 8 rpm. Some practical and theoretical implications are discussed.
The effects of increasing artificial gravity exposure on four aspects of physiological fitness are examined in four young men who, prior to exposure, were deconditioned with bed rest and water immersion. The four aspects of physiological fitness are orthostatic tolerance, exercise tolerance, forearm endurance, and maximum strength. Orthostatic tolerance was sharply reduced by deconditioning and was substantially improved by walking in simulated lunar gravity (1/6 g) for 2.5 hours daily for 7 days or by walking in 1/2 g and 1 g for 1 hour daily for 3 days. Exercise tolerance was also sharply reduced by deconditioning but did not significantly improve with increasing g-exposure. Walking in 1 g for 1 hour daily for 3 days raised exercise tolerance only a little above the low produced by deconditioning. Forearm endurance and maximum strength were relatively unaffected by deconditioning and subsequent g-exposure.
Explore the source record for details and available documents.
Twenty-four healthy men, 22 to 25 years of age, were exposed to stressful accelerations in a rotating room until acute mild motion sickness was elicited. Thirteen subjects in one group were exposed first with eyes open and later with eyes covered; the reverse order was used with the remaining eleven in the other group. The stressful accelerations were generated by requiring the subject to execute 120 standardized head movements at each 1-rpm increase in angular velocity until the desired endpoint was reached. When susceptibility to motion sickness with eyes open and covered is compared, 19 subjects were more susceptible with eyes open, three with eyes covered, and in the remaining two susceptibility was the same. The maximum difference in velocity between trial 1 and 2 was 7 rpm when susceptibility was greater with eyes open and 3 rpm when it was greater with eyes covered; the means, respectively, were 3.2 and 2.0 rpm. Among subjects manifesting greater susceptibility with eyes open than covered the group differences were small, indicating little or no adaptation effects. The findings are discussed mainly on the basis that vision may act also to decrease susceptibility under the stimulus conditions described.
Diagnosis criteria for grading severity of acute motion sickness applicable to empirical evaluation of clinical methods
Diagnostic criteria for grading severity of acute motion sickness
Fractional g levels for reducing effects of conditioning to zero gravity on prolonged space flights
Fractional g levels for reducing effects of conditioning to zero gravity on prolonged space flights